Regulator Ofcom found U.K. operator wrongly billed subscribers who called its customer support number.

EE was fined £2.7 million by U.K. telco regulator Ofcom on Wednesday for overcharging subscribers who called its customer support line.

An investigation found that customers who dialled the ‘150’ support number while roaming in the EU were billed as if they had called the U.S. It led to more than 32,000 customers being charged £1.20 (€1.38) per minute instead of £0.19 per minute.

According to Ofcom, EE decided not to reimburse the majority of affected customers until the regulator intervened, wrongly claiming it couldn’t identify those it overcharged, and so proposed to give the money to charity instead.

Ofcom’s investigation also found that despite making calls to 150 free within the EU from 18 November 2015, EE continued to bill some 7,600 customers up until 11 January 2016. On this occasion though, EE took prompt action and issued full refunds to those affected, Ofcom said.

"EE didn’t take enough care to ensure that its customers were billed accurately. This ended up costing customers thousands of pounds, which is completely unacceptable," said Lindsey Fussell, Ofcom’s consumer group director, in a statement.

Ofcom said the £2.7 million fine must be paid within 20 working days. The fine was reduced by 10% after EE agreed to settle the investigation, saving public money and resources. As part of the agreement, EE has taken full responsibility for the foul ups.

Furthermore, the majority of EE customers have now been refunded, except at least 6,905 who EE was unable to identify, who together were left £60,000 out of pocket. In lieu of a refund, EE has made a charitable donation of just under £62,000, Ofcom said.

"We monitor how phone companies bill their customers, and will not tolerate careless mistakes. Any company that breaks Ofcom’s rules should expect similar consequences," Fussell said.

Indeed, Wednesday’s EE fine comes months after Vodafone was hit with a £4.6 million penalty for issues experienced by prepaid customers resulting from the telco’s bungled migration to a new billing system.

As well as poorly-handling customer complaints, Vodafone mistakenly failed to credit the accounts of more than 10,000 customers, causing them to collectively lose £150,000 over a 17-month period.